Self-Monitoring and Self-Healing Bolted Joints Using Shape Memory Alloy

This paper describes the smart structural system using smart materials for real-time monitoring and active control of bolted joints in steel structures. The goal of research is to reduce the likelihood of failure and the cost of maintenance of the structures. This concept combines impedance based health monitoring techniques with shape memory alloy (SMA) washer to restore the loosen bolt’s tension. The impedance-based structural health monitoring (SHM) techniques has been used to detect loose bolts in the bolted joints. Through monitoring the measured electrical impedance and comparing it to a baseline measurement, the bolt loosening damage could be detected. Once loosening damage was detected in the bolted joint, the external heater which was bonded to SMA washer actuated the washer. Then the heated SMA washer expanded axially and adjusted bolt tension to restore lost torque. Experimental study was conducted by integrating piezoelectric material based structural health monitoring and SMA-based active control functions on a bolted joint, and the performance of a smart self monitoring and self-healing bolted joint system was demonstrated.